The present invention pertains to a copper alloy sputtering target capable of forming an interconnection material of a semiconductor device, particularly a stable and even seed layer during electroplating, and superior in sputtering deposition characteristics. The present invention also pertains to the manufacturing method of such a target.
Conventionally, although Al (resistivity of roughly 3.1 μΩ·cm) has been used as the interconnection material of a semiconductor device, low-resistivity copper interconnection (resistivity of roughly 1.7 μΩ·cm) has been put into practical application pursuant to the miniaturization of wiring.
As the current formation process of copper interconnection, after forming a diffusion barrier layer such as Ta/TaN to the concave portion of a contact hole or wiring groove, copper electroplating is often performed thereto. As the base layer (seed layer) for performing this electroplating, sputtering deposition is generally performed to copper or copper alloy.
The even formation of this base layer is important, and, if the base layer agglomerares, an even film cannot be formed upon forming a copper film with electroplating. For instance, defects such as voids, hillocks, disconnections and so on may be formed during the wiring.
Further, even if defects such as a void are not formed, an uneven copper electrodeposit will be formed at this portion, and a problem will arise in that the electromigration resistance characteristics will deteriorate.
In order to overcome this problem, it is important to form a stable and even seed layer during copper electroplating, and a sputtering target having superior sputtering deposition characteristics and being optimum for forming a seed layer will be required therefor.
Heretofore, as the copper interconnection material, a proposal has been made of adding certain elements to copper so as to improve the electromigration (EM) resistance characteristics, corrosion resistance, bond strength, and so on. For example, Japanese Patent Laid-Open Publication No. H5-311424 and Japanese Patent Laid-Open Publication No. H10-60633 disclose a pure copper target or a target to which 0.04 to 0.15 wt % of Ti is added to the pure copper.
And, in these proposals, it is proposed that rapid cooling be performed for the even dispersion of the added elements, or continuous casting be performed for preventing the segregation of the added elements in an ingot, ingot piping during casting, or enlargement of the crystal grains of the ingot.
Nevertheless, even if high purity copper is used alone or with minute amounts of metal added thereto, although there is an advantage in that the resistivity will be low, problems regarding electromigration and oxidation resistance during the process still remain, and these materials are not necessarily favorable materials.
In particular, since the aspect ratio is becoming higher (aspect ratio of 4 or higher) in recent days, sufficient electromigration resistance and oxidation resistance are required.
In light of the above, although a copper alloy sputtering target formed from high purity copper or with certain elements added thereto has been proposed, conventionally, this was not exactly sufficient.
Accordingly, an object of the present invention is to provide a copper alloy sputtering target capable of forming an interconnection material of a semiconductor device, particularly a stable and even seed layer during electroplating, and superior in sputtering deposition characteristics. Another object of the present invention is to provide a manufacturing method of such a target.